This application claims priority of Korean Patent Application No. 10-2004-0065384, filed on Aug. 19, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a turbine or a turbine generator, and more particularly, to a turbine or a turbine generator having adjustable vanes disposed at the turbine inlet area.
2. Description of the Related Art
Among many factors, maximum and minimum flow rates are typically considered in the design of turbines that are used for air compressors of fuel cells, auxiliary power units (APU), turbo chargers, and the like. In particular, an air compressor of a turbine power generator with a fuel cell should be capable of supplying air for a fuel cell stack at an adequate flow rate, pressure, and temperature. A coaxially coupled turbine may drive the air compressor. In this case, the turbine driving the air compressor should be driven at a proper speed regardless of the flow rate variation in a working fluid injected to the turbine wheel. In other words, when the flow rate of the working fluid is higher or lower than is required, the speed and pressure of the working fluid needs to be adjusted to drive the turbine at a designed speed, such that the air compressor coaxially coupled to the turbine can be driven at a selected speed, thereby obtaining a required amount of air flow from the air compressor to the fuel cell. For this purpose, adjustable (i.e., movable) inlet vanes are installed at a gas inlet area of the turbine to adjust the flow rate and pressure of the working fluid before the working fluid reaches the turbine wheel.
FIG. 1 is a schematic diagram showing a construction of a turbine generator having a turbine with adjustable vanes, according to a conventional art.
Referring to FIG. 1, a turbine generator includes an air compressor 2, a fuel cell 3, a burner 4, a turbine 10, and generator/motor unit 1. When the turbine generator starts operation, the generator/motor unit 1 may be used as a motor for driving the air compressor 2. In other words, the operation of the turbine generator is started by the generator/motor unit 1, and then the air compressor 2 is driven. The air compressor 2 takes in air and delivers the air to the fuel cell 3 at a high pressure. The fuel cell 3 allows the oxygen of the delivered air to react with hydrogen supplied from the burner 4 such that electric power and high-temperature gas are produced. The pressure of the high-temperature gas is also high. The gas is used as the working fluid of the turbine 10. The burner 4 additionally burns the gas produced from the fuel cell 3 to increase the temperature of the gas up to a temperature required at the turbine 10. The working fluid burnt at the burner 4 flows to the turbine 10. Electric power generated from the fuel cell 3 is delivered to a three-phase system.
Generally, the turbine 10 includes vanes and a turbine wheel 7, in which the vanes control the working fluid flowing into the turbine. The vanes of the turbine 10 coaxially coupled with the air compressor 2 are adjustable vanes 6. The adjustable vanes 6 allow the working fluid to collide with the turbine wheel 7 at a desired pressure and flow rate, such that the energy of the working fluid can be converted into a mechanical energy for rotating the shaft to which the turbine wheel 7 is fixed.
The generator/motor unit 1 includes a magnetic rotor (not shown) coupled with the shaft of the turbine wheel 7 and a stator (not shown) forming a magnetic field around the magnetic rotor. The magnetic rotor starts to rotate by the rotation of the shaft of the turbine wheel 7, and this rotation of the magnetic rotor disturbs the magnetic field formed by the stator and a current is produced at the rotor, thereby enabling the generator/motor unit 1 to function as a generator.
FIG. 2 is a schematic and plan view of a turbine with movable or adjustable inlet vanes (hereinafter called as “adjustable vane turbine”) according to one example of the prior art. Referring to FIG. 2, adjustable vane turbine 10 includes the turbine wheel 7 at a center, adjustable vanes 61 around the turbine wheel 7, and turbine blades 71 located around the turbine wheel 7. The adjustable vanes 61 are uniformly arranged around a turbine housing (not shown), and each adjustable vane 61 has one end portion rotatably coupled to the housing. A hydraulic system (not shown) controls the adjustable vanes 61 to rotate at the same angle with respect to the turbine housing. The hydraulic system includes a sensor detecting the flow rate of the working fluid and other hydraulic devices such as a hydraulic actuator. The hydraulic system uses the actuator to rotate the adjustable vanes 61 according to the flow rate detected by the sensor, such that the hydraulic system can control the amount of working fluid colliding with the turbine blades 71 of the turbine wheel 7 by rotating the adjustable vanes 61. It is disadvantageous to use the hydraulic system because the hydraulic system requires a higher manufacturing cost and has a nonlinear property having difficulties in controlling the system and complexities in designing the controller.